The prior art discloses many ashless dispersants useful as additives in fuels and lubricant compositions. A large number of such ashless dispersants are derivatives of high molecular weight carboxylic acid acylating agents. Typically, the acylating agents are prepared by reacting an olefin (e.g., a polyalkene such as polybutene) or a derivative thereof, containing for example at least 30 to 50 aliphatic carbon atoms, with an unsaturated carboxylic acid or derivative thereof such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and maleic anhydride. Dispersants are prepared from the high molecular weight carboxylic acid acylating agents by reaction with, for example, amines characterized by the presence within their structure of at least one N-H group, alcohols, reactive metal or reactive metal compounds, and combinations of the above. U.S. Pat. No. 4,234,435 summarizes some of the prior art relative to the preparation of such carboxylic acid derivatives.
It also has been suggested that the carboxylic acid derivative compositions such as those described above can be post-treated with various reagents to modify and improve the properties of the compositions. Acylated nitrogen compositions prepared by reacting the acylating reagents described above with an amine can be post-treated, for example, by contacting the acylated nitrogen compositions thus formed with one or more post-treated reagents selected from the group consisting of boron oxide, boron oxide hydrate, boron halides, boron acids, esters of boron acid, carbon disulfide, sulfur, sulfur chlorides, alkenyl cyanides, carboxylic acid acylating agents, aldehydes, ketones, phosphoric acid, epoxides, etc. Lists of the prior art relating to post-treatment of carboxylic ester and amine dispersants with reagents such as those described above are contained in a variety of patents such as U.S. Pat. Nos. 4,203,855 (Col. 19, lines 16-34) and 4,234,435 (Col. 42, lines 33-46).
U.S. Pat. No. 3,216,936 describes lubricant additives which are compositions derived from the acylating of alkylene polyamines. More specifically, the compositions are obtained by reaction of an alkylene amine with an acidic mixture consisting of a hydrocarbon-substituted succinic acid having at least about 50 aliphatic carbon atoms in the hydrocarbon group and an aliphatic monocarboxylic acid, and thereafter removing the water formed by the reaction. The ratio of equivalents of said succinic acid to the mono-carboxylic acid in the acidic mixture is from about 1:0.1 to about 1:1. The aliphatic mono-carboxylic acids contemplated for use include saturated and unsaturated acids such as acetic acid, dodecanoic acid, oleic acid, naphthenic acid, formic acid, etc. Acids having 12 or more aliphatic carbon atoms, particularly stearic acid and oleic acid, are especially useful. The products described in the '936 patent also are useful in oil-fuel mixtures for two-cycle internal combustion engines
British Pat. No. 1,162,436 describes ashless dispersants useful in lubricating compositions and fuels. The compositions are prepared by reacting certain specified alkenyl substituted succinimides or succinic amides with a hydrocarbon-substituted succinic acid or anhydride. The arithmetic mean of the chain lengths of the two hydrocarbon substituents is greater than 50 carbon atoms. Formamides of monoalkenyl succinimides are described in U.S. Pat. No. 3,185,704. The formamides are reported to be useful as additives in lubricating oils and fuels.
U.S. Pat. Nos. 3,639,242 and 3,708,522 describe compositions prepared by post-treating mono- and polycarboxylic acid esters with mono- or polycarboxylic acid acylating agents. The compositions thus obtained are reported to be useful as dispersants in lubricants and fuels.
U.S. Pat No. 4,780,111 describes fuel compositions containing a hydrocarbon-soluble dispersant prepared generally by the post-treatment of a nitrogen-containing composition with mono- and polycarboxylic acids which may be aliphatic or aromatic carboxylic acids, preferably the latter. The nitrogen-containing compositions which are post-treated in accordance with U.S. Pat. No. 4,780,111 are obtained by reacting an acylating agent with alkylene polyamines or alkanol amines. The patent reports that when such fuel compositions are utilized in internal combustion engines, and in particular, fuel-injected internal combustion engines, the amount of solid deposits on the various parts of the internal combustion engines are reduced.
Use of such post-treatment procedures adds to the complexity of the production process and to the cost of the product so formed.